Carpal tunnel syndrome is among the most frequently encountered neuro-musculoskeletal disorders. Initially described by Sir James Paget in 1853, the syndrome of median nerve entrapment has been recognized traditionally as primarily a disease of middle life. Recently however, its incidence and prevalence have been increasing among both younger persons and those beyond middle life.
The increase in occurrence of carpal tunnel syndrome has been coincident with a number of factors including lengthening life expectancy. However, a particularly significant factor appears to be the ubiquity of the computer keyboard in both the home and the office. Indeed, because of the wide spread use of the computer in the home and in clerical and office employment, the incidence of carpal tunnel syndrome has increased dramatically. Moreover, it is estimated that afflicted females out number males at a ratio of from 3:1 to 5:1.
The carpal tunnel is a semi-nondistensible, open-ended and approximately cylindrical anatomical compartment bounded by the carpal bones and the flexor retinaculum, a.k.a. the flexor carpal ligament. The carpal tunnel is situated beneath the soft tissues at and just proximal to the wrist, with its long axis parallel with the axial plane of the arm. The carpal tunnel is traversed by the flexor tendons of the hand, the vascular supply of the median nerve and the median nerve itself. The median nerve supplies sensory and motor functional innervations to a substantial and rather distinct portion of the human hand. In the transverse plain, at the level of the distal forearm, the median nerve lies immediately beneath the flexor retinaculum; the flexor tendons to the hand lie deep to the median nerve.
The median nerve is the softest structure within the carpal tunnel, and when intraluminal pressure becomes augmented or increased, the vectors of force are exerted upon and against the median nerve and its blood supply. Patients with carpal tunnel syndrome suffer from elevated intraluminal pressure, such as that resulting from inflammation due to a myriad of potential underlying pathophysiological etiologies, or all too often, without any apparently identifiable reason. Specifically, where intraluminal pressure within the carpal tunnel increases, the consequential impingement of the median nerve and its blood supply leads to circulatory compromise in the median nerve. This compromise in blood flow in turn, slows the rate of median neural conduction which is manifested by an objective functional impairment of the hand. This impairment may be acutely exacerbated by certain mechanical stresses.
The most frequent complaints of carpal tunnel syndrome are hand pain and a numbness characterized by the classic "text book description" of carpal tunnel syndrome which includes: burning, nocturnal hand pain, which generally is sufficient to awaken the patient from sleep, and which may be temporarily relieved by shaking or suspending the hand and forearm in a dependent position. This pain may also radiate proximally to the forearm or elbow, and, at times, even as far as the shoulder. Numbness occurs along the distribution of the median nerve, which includes the anterior surfaces of the thumb, index finger, middle finger, and the radial half of the ring finger, as well as the distal palm. Loss of tactile sensation or thenar muscle atrophy often results in patient complaints of clumsiness or incoordination of the affected hand(s). Muscular wasting is a relatively late phenomenon in the development of the carpal tunnel syndrome disease process.
Traditionally, treatments employed for carpal tunnel syndrome have been classified as either curative or palliative. Of the curative treatments, surgical release and decompression is considered the only viable and therefore accepted method. One example of a recent development in the surgical treatment of carpal tunnel syndrome is disclosed in U.S. Pat. No. 5,089,000 to Agee et. al. However, even an intervention so seemingly definitive as surgery does not enjoy unequivocal success as propitious therapy for carpal tunnel syndrome. Although conventional operative release and decompression of the carpal tunnel has been deemed the only curative modality available, it appears that surgical success, as that term is used in authoritative text in professional journals describe operative results or outcomes which fall short of permanent abatement of all clinical manifestations of carpal tunnel syndrome. It is estimated that as many as approximately 30% of the cases treated via surgery have failed that modality. In other words, surgical success and operative cure are not synonymous terms in the applicable literature.
Even in those published reports which fail to specifically delineate qualifications for successful surgical treatment, a low threshold for categorization of a surgical result as successful may be inferred from the usual very narrow definition of a surgical failure. Most often a case is considered to have failed surgically where no identifiable improvement occurs immediately after surgery, or where symptoms recur during the proximate post-operative convalescent period.
Moreover, because the surgical methods used to treat carpal tunnel syndrome necessarily give rise to some tissue damage and scarring in or about the carpal tunnel, the resultant inflammatory response increases intraluminal pressure post-surgically. This increase in some individuals is permanent, thereby exacerbating this condition in a number of patients.
In sum, surgical treatment for carpal tunnel syndrome, although potentially curative in some cases, is probably more often in reality, a palliative technique which is ineffective in a large fraction (up to 30%, or more over time) of patients. Clearly, operative management of carpal tunnel syndrome has a number of inevitable and potential drawbacks all of which are self-evident.
Carpal tunnel syndrome has recently become the second leading cause of time lost from work due to disability. Employment-related carpal tunnel syndrome presents a number of heretofore unresolved problems relating to a number of factors. Central among these factors is that no known therapeutic modality adequately treats the problem. Specifically, for example, following surgery for employment-associated carpal tunnel syndrome, the patient-employee suffers early reoccurrence of his/her symptoms, even where the work load and duration of work stress have been dramatically reduced. The relevant medical literature has not offered any substantial explanation or recommendation therefore directly. However, two relatively contemporaneous reports, do explain the situation. For example, computerized axial tomography (CAT) scans of the carpal tunnel were obtained before and after surgery for work-related carpal tunnel syndrome. The CAT scans demonstrated that, following division of the flexor retinaculum, the contents of the carpal tunnel subluxed distally and palmarly. Considering this displacement in light of the poor results following carpal tunnel syndrome surgery, in work-related cases, it can reasonably be inferred that such surgery, in fact, places the median nerve and other carpal tunnel contents in a position more vulnerable to the forces causing the malady in the first place, yet without the buffering protection of the intact flexor-retinaculum.
Although a number of palliative measures have been advanced as alternatives to surgical intervention, these measures provide very limited, if any, therapeutic benefits. Palliative therapies include for example, volar, i.e., palmar or anterior, splinting, short-arm and transversing the wrist joint; elevation of the wrist; administration of non-steroidal anti-inflammatory drugs, e.g., aspirin, indomethacin and ibuprofen and their progeny; diuretic agents which may be prescribed intermittently; and administration of corticosteroid drugs. Any limited benefits that palliative therapies can provide are provided only very early on in the course of carpal tunnel syndrome or where carpal tunnel syndrome is present in its mildest form. Thus, the effectiveness of palliative therapy is at best, inconsistent, transient or equivocal, and at worst, may be harmful to the patient.
Corticosteroid administration is perhaps the most interventional and controversial among the various palliative measures traditionally employed in the treatment of carpal tunnel syndrome. Towards this end, investigators and clinicians have administered corticosteroid agents both systemically, by mouth or parenterally, and locally, by injection. Regardless of the route or cite of steroid administration employed in the therapeutic endeavor, authoritative texts which speak to this matter have generally been uniformly unenthusiastic in describing the efficacy of corticosteroid drugs in the management of carpal tunnel syndrome.
Since the time corticosteroid injection therapy was first employed in the management of carpal tunnel syndrome over three decades ago, virtually the identical methodology and location of that technique has been repeatedly adopted, without any material change or refinement. Technically, the traditional injection technique as recorded in the medical literature is neither a site specific injection nor a treatment of carpal tunnel syndrome, but merely a local injection at the wrist utilized as a palliative measure in the presence of median nerve entrapment. As shown in photographs and drawings contained within reported medical literature, the traditional mode of injection deposits medication approximate to the median nerve at a point near, at, or beyond the entrapped nerve's exit from the distal canal.
Review of the particular corticosteroid agents and their dosages employed in traditional corticosteroid injections for carpal tunnel syndrome reveals that these drugs are generally short-acting, often of only mild-to-moderate potency, or are administered in inadequate doses. Significantly however is that the direction of conventional injections is the same as the direction of the flow of the blood and synovial fluid. This not only carries the instillant away from the carpal tunnel, but also, since it is proximate to a rich vascular arcade, this type of injection hastens its removal from the site of its local injection into the systemic circulation. This, in no small way, contributes to the transient nature of whatever benefits might be conferred.
Finally, traditional corticosteroid injections are performed only by a limited number of medical specialists, most of whom are the same physicians who perform the carpal tunnel release surgery. A number of potential complications of corticosteroid injection have been advanced; the most serious of which are impalement of the median nerve and chemical neuritis.
It can be seen from the foregoing that it is desirable to have nonoperative techniques and instrumentalities for the treatment of carpal tunnel syndrome which are substantially more effective to those methods of treatment currently used.
It is an object of the present invention to provide techniques and devices for the treatment of carpal tunnel syndrome which are viable alternatives to surgical treatment methods and eliminate the risk and complications associated with carpal tunnel syndrome surgery, in appropriate patients (which includes the majority).
It is also an object of the present invention to provide patients with greater accessibility to effective therapy for the treatment of carpal tunnel syndrome.
Yet another object of the present invention is to provide a method of treatment for carpal tunnel syndrome which significantly reduces the cost of healthcare associated with its treatment.
Still another object of the present invention is to provide a treatment method for carpal tunnel syndrome which eliminates the peri-operative patient pain, inconvenience, and prolonged recuperation associated with traditional treatment methods.
Another object of the present invention is to provide a treatment modality which is effective in cases considered to be prognostically poor for or which have failed surgery.
Yet another object of the present invention is to provide an effective non-surgical treatment method for carpal tunnel syndrome which may be performed by a variety of medical specialists.
These and other objects of the present invention are fulfilled by the novel technique and instrumentality set forth herein.